For conventional elevator systems there are various control methods which perform favorable distribution of the travel orders among the available elevator cars. For this purpose, the travel requests by the passengers when they press a request key are collected and administered by a control unit. In simple systems, it is merely decided which car will be the next to serve the corresponding story, and in advanced systems with what is referred to as “destination selection control”, the travel orders are bundled at the known start position of the passenger and the desired destination position. The passengers must in this case input their travel destination on an operator keypad before they enter the car. Furthermore, the control methods usually take into account different peripheral conditions such as e.g. the expected overall travel time for a passenger or the maximum waiting time of a passenger.
Elevator shafts are frequently already organized into groups when planning buildings, wherein certain groups serve predetermined areas of stories respectively. In buildings with a particularly large passenger volume, express elevators are also provided which serve individual stories. The passengers must then, under certain circumstances, change elevators in order to reach their destination. Such groupings of elevator shafts serve to dissipate traffic flows, but result in large expenditure in terms of construction technology and require a large amount of space.
The conventional elevator systems can be differentiated according to the number of elevator cars per shaft. Most conventional elevator systems have in common the fact that in each case just one car is located in a shaft. Therefore, there are no peripheral conditions or restrictions whatsoever in respect of the travel orders of the cars in relation to one another.
In so-called multicar elevator systems, two or more cars move in one shaft. An example of this is the “TWIN” elevator system by the applicant in which case two cars are located in one shaft respectively and can move independently of one another. The control method of this system is based on the destination selection control already mentioned and said system organizes the cars into groups in such a way that the respective upper car in each shaft is used to serve the upper stories, and the respective lower car is used to serve the lower stories. During the apportioning of the travel orders, it is taken into account as a peripheral condition that the two cars in each shaft must not impede one another.
There is extensive patent literature on control methods for elevator systems with two or more elevator cars per shaft and/or multiple shafts.
U.S. Pat. No. 6,955,245 B2 describes an elevator system with three shafts, in which two or more elevator cars are located. The three shafts are divided into one shaft for upward journeys, a further shaft for downward journeys and a shaft for parking elevator cars. In the case of increased travel requests, for example a third elevator car is transferred into the shaft for upward journeys or downward journeys. After the corresponding travel orders have been executed, the empty car can be transferred into the parking shaft at the next transfer station.
US 2010/0078266 A1 describes an elevator system with at least one shaft and at least two cars which can be moved independently of one another in a shaft. A described example uses two cable elevator cars. These can move in the same direction or in the opposite direction. Sensors for the load, speed and distance between the cars are present and they transmit corresponding signals to a control unit. The central control then controls the cars as a function of the sensor signals, depending on travel orders.
DE 37 32 240 C2 describes an elevator system with a plurality of elevator shafts which each serve different areas of stories. When there is a high traffic volume, the departures of the elevator cars which have stopped at a transfer floor are delayed so that a sufficient number of passengers can enter.
EP 1 440 030 B1 discloses an elevator system with at least two elevator shafts, wherein transfer levels for changing between the shafts are present, in order to serve specific areas of stories. Each shaft is divided into what are referred to as local shafts in which the elevator cars can move independently of one another.
US 2003/0098208 A1 discloses an elevator system with shafts in each of which two elevator cars can move. The requested destination positions are administered and each of the two elevator cars is assigned its own zone and a common zone of stories. The common zone can be travelled through only by an elevator car if no impedance with other cars can occur wherein after the corresponding travel order has been executed, the common zone has to be exited again.
U.S. Pat. No. 5,107,962 A relates to an elevator system with a shaft in which two or more elevator cars can move, wherein the cars are each cable elevator cars. For example, here two elevator cars are arranged, and can move, one next to the other in an upper shaft part, while a further elevator car can move in a lower shaft part.
EP 2 341 027 B1 proposes a method for controlling an elevator system with at least one shaft in which at least one elevator car for transporting persons and/or loads can be moved by means of a drive device, and with an elevator control device which controls the operation of the elevator system, wherein usage data of the elevator system is collected over a predefined collection time period and evaluated, and the operation of the elevator system is controlled predictively as a function of collected usage patterns, in a way which is optimized in terms of energy and/or transportation capacity.
EP 2 307 300 B1 discloses a method for controlling an elevator system with a plurality of elevator cars per elevator shaft on the basis of the already mentioned destination selection control. In this context, the operation of the elevator system is controlled with particular consideration for passengers with impairments, by means of what is referred to as an impairment parameter.
WO 2007/024488 A2 relates to the control of a twin elevator system as already mentioned above, with a plurality of shafts and a plurality of elevator car pairs, wherein an elevator car is respectively assigned a specific zone of the corresponding shaft.
WO 2004/048243 A1 also discloses a method for controlling a twin elevator system with a destination selection control. If a destination call relates to the common travel way along which two elevator cars can be moved separately upward and downward, the travel way section which is necessary to service the destination call is assigned to an elevator car and the other elevator cars are blocked for the time of the assignment. The control method according to WO 2004/048244 A1 is based on the same elevator system and on the same principles as those of WO 2004/048243 A1.
EP 0 769 469 B1 relates to what is referred to as a multi-mobile elevator group with a plurality of shafts and a plurality of elevator cars, wherein each car is driven by a separate independent drive and provided with a separate brake. The shafts are respectively connected at their upper and lower ends to one another by a connecting passage. In this way, the cars can change their direction of travel by changing shaft. The direction of travel of a car can also change within a shaft. In order to increase the efficiency and the safety of this elevator system it is proposed in this document that each car be equipped with a separate safety module which can trigger braking processes both in its own car and in adjacent cars, wherein the safety module calculates the necessary braking behavior of the cars from current travel data of the cars on the basis of stop enquiries, and collisions between cars are therefore prevented.
WO 2008/136692 A2 discloses a cyclical multi-car elevator system with a upward-leading shaft and a downward-leading shaft and a plurality of elevator cars which can be moved upward and downward in these two shafts. At the two ends of these shafts there are transfer stations by means of which the cars can be transferred in the horizontal direction from one shaft to the other shaft. These stations can also be configured to supply additional cars when required. Furthermore, stations which are located between the two shafts may be present for taking out of circulation a car which is, for example, defective. This cyclical multi-car elevator system can be scaled to the respective requirement. Individual details on the control method of this multi-car elevator system are not given in this document.
A cyclical multi-car elevator system in the style of a paternoster was filed by Hitachi in EP 1 647 513 A2. In this system, a plurality of elevator cars circulate in a upward-leading shaft and in a downward-leading shaft, the two ends of which shafts each constitute transfer stations with individual cars from one shaft into the other shaft. In each case two cars are coupled to one another by means of cable drives, with the result that, for example, when one of the two cars is located in the upper part of the elevator upward-leading shaft, the other of the two cars is located in the lower part of the downward-leading shaft. A plurality of such elevator car pairs are accommodated in the two shafts by means of a special steel-cable drive system. Each elevator car of such a pair of elevator cars serves as a counterweight for the respective other elevator car. Individual pairs of elevator cars can be operated independently of the other pairs, permitting mutual impairment to be ruled out.
The principle of the cyclical multi-car elevator system has the advantage of requiring little space, since in principle only two elevator shafts are required, wherein a plurality of elevator cars can be accommodated in the respective shafts, in order to achieve a largest possible transportation capacity.